Accident Blackspot Investigation Handbook

Republic of the Philippines

DEPARTMENT OF PUBLIC WORKS AND HIGHWAYS

Accident Blackspot Investigation Handbook

Project Preparation for the Accident Backspot Program


Table of Contents PART 1

INTRODUCTION ................................................................................................1

Context ...........................................................................................................................1 Purpose and Scope of this Handbook ............................................................................1 Structure of the Handbook..............................................................................................1 PART 2

THE PROJECT CYCLE .....................................................................................3

Step 1: Identify Hazardous Locations............................................................................4 Step 2: Investigate the Hazardous Locations ................................................................4 Step 3: Formulate Candidate Projects...........................................................................5 Step 4: Screen-out Ineligible Projects ...........................................................................5 Step 5: Appraise the Project Economics .......................................................................6 Step 6: Prioritize the Projects ........................................................................................6 Step 7: Deliver the Project.............................................................................................7 PART 3

PREPARATION OF ROAD ACCIDENT REDUCTION PROJECTS..................8

STEP 1 – Identify Hazardous Locations.........................................................................8 Step 1.1

Analyze Accident Data ......................................................................9

Step 1.2

Review Locations Nominated from Other Sources..........................10

Step 1.3

Compile Listings of Worst Accident Locations.................................10

Step 1.4

Select Sites for Investigation ...........................................................10

Step-by-Step Guide ..........................................................................................11 STEP 2 – Investigate Hazardous Locations .................................................................13 Step 2.1

Collect the Accident Data ................................................................14

Step 2.2

Presentation of the Accident Data ...................................................15

Step 2.3

Analyze the Accident Data ..............................................................17

Step 2.4

Inspect the Accident Site .................................................................18

Step 2.5

Review the Information and Formulate Conclusions .......................19

Step-by-Step Guide ..........................................................................................19

Accident Blackspot Investigation Handbook.doc

Page i


STEP 3 – Formulate Candidate Projects......................................................................21 Step 3.1

Identify Treatment Options ..............................................................21

Step 3.2

Develop a Preliminary Treatment Proposal.....................................25

Step 3.3

Review Site Constraints and Modify Treatment Proposal ...............28

Step 3.4

Prepare Concept Design Plan .........................................................29

Step 3.5

Prepare Cost Estimate ....................................................................29

Step 3.6

Write an Accident Blackspot Report ................................................30

Step-by-Step Guide ..........................................................................................30 APPENDICES .......................................................................................................................33

APPENDIX A Typical TARAS Rank report & map of accident locations.

APPENDIX B Example of TARAS Listing report

APPENDIX C Example of TARAS Summary Report

APPENDIX D Sample of a completed Traffic Accident Report (TAR)

APPENDIX E Chart of Traffic Accident Descriptions (TAD) codes

APPENDIX F Typical Accident Factor Chart

APPENDIX G Typical Site Inspection Field Notes format

APPENDIX H Sample preliminary cost estimate

APPENDIX I Typical Accident Blackspot Report Format

APPENDIX J Accident Blackspots Ranking Spreadsheet for Site Data and Project Evaluation


Page ii


Glossary of Terms Accident Rate

number of major accidents per year for intersections and short mid-block sections (less than 500 meters) or major accidents per year per km for road sections longer than 500 meters

Accident Factor Chart

a tabular format of presentation of key information about each accident at an intersection or section of road

Blackspot

intersection or road section which has a high accident rate

Blackspot Project

road accident reduction project at a blackspot

CBA

Cost-Benefit Analysis – a technique for calculating an indicator of the economic merit of a project

Clear Zone

the unobstructed, relatively flat area provided beyond the edge of the traveled way for the recovery of errant vehicles (includes any shoulders or auxiliary lanes)

Collision Diagram

a diagrammatic representation of accidents that have occurred at an intersection or along a road section

Hazardous Location

blackspot – intersection or road length which has a high accident rate

Hazardous Location Report

a report that documents the outcome of the investigation of a hazardous location and provides details of the resulting proposed candidate blackspot project

MCA

Multi-criteria Analysis – a technique for prioritizing projects on the basis of several decision criteria

National Road Network

the roads for which the Department of Public Works and Highways is responsible

Road Accident

a localized infrastructure and/or traffic management treatment specifically

Reduction Project

designed to make the road safer to use

TAD

Traffic Accident Description – a numerical code assigned to each accident type

TAR

Traffic Accident Report – a form that is filled in by the attending police officer at the scene of an accident to record details of the accident

TARAS

Traffic Accident Recording and Analysis System – a database in which details of accidents on the National Road Network are recorded and analyzed

Treatment

road works or traffic management measures implemented at a particular site to reduce road safety hazards at that location

Injury Types Fatal Injury

an injury resulting in death within 30 days of the road accident

Serious Injury

an injury that is serious enough to require admission to hospital, but is not fatal

Minor Injury

an injury that requires medical attention, but not admission to hospital

Accident Types Fatal Accident

an accident in which at least one person is killed (within 30 days of the accident)

Serious Injury Accident

an accident in which at least one person is admitted to hospital (but nobody is killed)

Minor Injury Accident

an accident in which at least one person is injured (but nobody is killed or seriously injured)

Property Damage Only

an accident where nobody is injured but vehicles or other property is damaged

Major Accident

a road accident in which someone is killed or injured seriously enough to be admitted to hospital for medical treatment. These are ‘high severity’ accidents in TARAS.

Minor Accident

a road accident that involves only minor injuries and property damage – nobody is killed or seriously injured


Page iii


PART 1

INTRODUCTION

Context Road accidents affect the lives of tens of thousands of Filipinos each year and cost the country billions of pesos each year in lost economic output. In many cases, making small changes to the design and construction of the road and the way traffic is managed can significantly reduce the risk of road accidents at a particular location.

Purpose and Scope of this Handbook This Handbook describes procedures for identifying and investigating hazardous, or blackspot, locations and developing road accident reduction projects – localized, relatively low-cost infrastructure and traffic management projects specifically designed to make the roads safer to use. The procedures are designed to provide a systematic approach to the identification and investigation of accident blackspots and the development of candidate projects that can be considered for inclusion in the Road Accident Reduction Program. The objective of the procedures described in the Handbook is to produce candidate projects for the Road Accident Reduction Program that will effectively reduce the incidence and / or severity of major accidents at the worst accident locations on the national arterial road network. The Handbook contains information on the use of accident data, reports and maps from the Traffic Accident Recording and Analysis System (TARAS) to identify hazardous locations and assist with the analysis of accident patterns and causal factors at particular sites. However, it does not provide guidance on the use of TARAS – readers should refer to the TARAS Users Manual for this purpose. The Handbook provides guidance on the critical steps required to investigate and develop a project comprising engineering countermeasures that will have a high probability of improving road safety at a blackspot location. It therefore is aimed at developing an understanding of the factors that contribute to road accidents as well as knowledge of which treatments will be the most effective in addressing different accident types and patterns. The scope of this Handbook extends to the point in the project cycle at which a road accident reduction project has been developed to the concept design stage with a preliminary cost estimate. Beyond this point, candidate projects will be submitted for evaluation, including screening to ensure compliance with the criteria for acceptable road accident reduction works, economic appraisal using cost-benefit analysis and prioritizing using a multi-criteria analysis methodology. Procedures for these steps in the project cycle are contained in the companion Handbook – Road Accident Reduction Program: Project Evaluation Handbook. Other manuals that provide guidelines on specific aspects of road safety include the Road Safety Audit Manual and Highway Safety Design Standards Manual.

Structure of the Handbook The Handbook is structured into several parts: PART 1

describes the context, purpose and scope of the Handbook.

Page 1


PART 2

puts the project preparation phase into context within the overall project cycle of project preparation, evaluation and delivery. This part of the Handbook provides an overview of each of the steps in the project cycle for road accident reduction projects; covering identification of hazardous locations, through site investigation, formulation of treatment options, screening-out of unsuitable projects, economic appraisal, multi-criteria evaluation of each candidate and ranking of projects in priority order, culminating in delivery of funded projects.

PART 3

provides a step-by-step guide to the project preparation process for road accident reduction projects, including: the identification of blackspots using TARAS and other sources; investigation of hazardous locations to determine accident patterns and contributing factors; and the development of candidate projects comprising accident countermeasures to reduce the incidence of accidents.

APPENDICES provide examples of accident reports etc. from TARAS and samples of other information and tools used in the accident blackspot investigation and project development process.

Page 2


PART 2

THE PROJECT CYCLE

This Part of the Handbook puts the task of project preparation into context within the overall project cycle of the project preparation, evaluation and delivery cycle. Because all of the phases in the cycle are linked, it is important to understand where the project preparation phase fits within this overall process. The key steps in the process are shown in the following diagram.

PREPARATION

1. IDENTIFY hazardous locations

Hazardous Locations

2. INVESTIGATE hazardous locations

Potential Projects

3. FORMULATE candidate projects

Eligible Projects

EVALUATION

4. SCREEN projects against eligibility criteria

Candidate Projects

5. APPRAISE project economics

Cost-benefit Assessment

DELIVERY

6. PRIORITIZE using multicriteria score

Prioritised List of Projects

7. DELIVER projects

The steps are: 1. Identify locations where accidents are occurring at an above-average rate; 2. Investigate the locations which, on the basis of available information, have been identified as having high accident risk; 3. Formulate a project of road safety treatments for each site based on the results of a detailed investigation of the site; 4. Screen out projects that fail to meet the minimum criteria for an acceptable project for road accident reduction works; 5. Appraise the economics of the project using cost-benefit analysis; 6. Prioritize the projects using a multi-criteria analysis methodology; 7. Deliver the road accident reduction project.

Page 3


Each of these steps is briefly explained in the following sections of Part 2. Then in Part 3 of this Handbook, the steps in the project preparation phase of the cycle are explained in stepby-step detail. A detailed explanation of steps in the Project Evaluation phase is provided in the Road Accident Reduction Program: Project Evaluation Handbook.

Step 1: Identify Hazardous Locations The first step in the project cycle is to identify hazardous locations. For convenience, this Handbook uses the term blackspot to refer to all types of hazardous locations with a high road accident risk, including: •

intersections which have a higher than average accident rate;

•

road sections which have a higher than average accident rate; and

•

small areas with a higher than average accident rate.

Possible blackspots can be identified from a variety of sources – they can be: •

identified through statistical analysis of accident records, for example, by using TARAS;

•

suggested by DPHW Regional or District engineers; or

•

suggested by the community or local government officials.

The aim of this Step is to identify all locations with a poor record of road safety. The criteria to be used for identifying blackspots to be considered for treatment projects is set out in Part 3 (Table 3.1) of this Handbook. Note that the criteria focus on major accidents, since these are the accidents that have the greatest impact on the community as a result of fatal and serious injuries. At this Step in the project cycle, the aim is to draw on all sources to identify all locations with a poor road safety record and prepare a list of hazardous locations that will be considered for treatment action. All suggestions should be included in the list of hazardous locations. A step-by-step guide to identifying hazardous locations is provided in Part 3 of this Handbook.

Step 2: Investigate the Hazardous Locations The second step is to investigate the sites. In general, it will not be possible to investigate all of the hazardous locations identified in Step 1 because of the likely large number of sites and limited resources and time. As a general guide, priority should generally be given to investigating sites where people are being killed or seriously injured rather than sites with a history of large numbers of minor accidents. This means giving priority to investigating the locations with the highest average number of major accidents per year. The aim of the site investigation is to gather information that can be used to verify the level of safety risk at the location and formulate a response. Information required from the site investigation includes: •

confirmation of accident frequency and severity

•

predominant accident type and probable cause(s) of accidents

•

physical geometry of the site (layout of intersections and road sections)

•

location environment (roadside structures, adjacent land use, environment)

•

traffic volume and composition

Page 4


•

driver behavior

•

other relevant information about traffic and road use.

A step-by-step guide for investigating hazardous locations is provided in Part 3 of this Handbook.

Step 3: Formulate Candidate Projects Having identified and investigated a blackspot location, the next step is to formulate a proposal for reducing the level of accident risk. In most cases, this will involve formulating a project that will involve one or more engineering treatments. In some cases, the proposal to reduce accident risk may also include recommendations for enforcement and/or community education to address matters relating to driver behavior. The types of treatment should be matched to the location and accident trend profile, taking into consideration: •

site and traffic conditions (such as right of way, pavement conditions, sight distance etc);

•

effectiveness of the treatment in reducing accident frequency and severity;

•

appropriateness of the treatment in the context of road environment and road network at each location; and

•

preliminary estimated cost of the treatment.

Detailed information on selecting and designing road safety treatments is contained in the Section 3 of this Handbook. For the purposes of evaluating and prioritizing blackspot improvement projects, the outputs from the project formulation step must include: •

a description or concept plan of the proposed treatment;

•

a preliminary estimate of the cost of the treatment works;

•

whether or not the works will require land acquisition and resettlement of persons living on the site;

•

whether or not there will be significant environmental impacts such as major earthworks, changes to drainage patterns, disturbance of native forests and wildlife etc; and

•

an estimate of the number of vehicles that pass through the site each day (AADT from traffic counts if possible, or a realistic estimate of traffic volume).

A step-by-step guide to formulating candidate projects is provided in Part 3 of this Handbook.

Step 4: Screen-out Ineligible Projects In some cases, a proposed road safety project can have adverse social, environmental or other implications or be inconsistent with other road development plans for the area. This can mean that the proposed project is not an acceptable solution to the road safety problem and is unlikely to be implemented regardless of its other merits. The purpose of this step is to screen out and review those projects that have serious drawbacks. This avoids wasting scarce resources on detailed evaluation of potential projects that have little realistic chance of being implemented. Screening of projects can also avoid a situation where funds may be allocated to a project that is not feasible or cannot be implemented for various reasons.

Page 5


The projects that fail to meet the eligibility criteria can then be reviewed and either: •

reformulated in a way that avoids the original drawbacks, typically, by finding a different solution to the road safety problems; or

•

removed from further consideration if no acceptable alternative solution can be found to rectify the problems with the project.

Procedures for screening out ineligible projects are described in the Road Accident Reduction Program: Project Evaluation Handbook.

Step 5: Appraise the Project Economics Potential projects that pass through the screening process (Step 4) are then evaluated in detail. In general, the aim of evaluating projects is to find the projects that provide the most cost-effective way of allocating money – that deliver the best return from every peso spent. In the context of road accident reduction projects, this means delivering the greatest reduction in road safety risk and greatest reduction in numbers of accidents for the lowest cost. The purpose of this step in the evaluation process is to calculate an indicator (a number) that measures the overall economic merit of the project. This economic indicator then becomes a key input to the process for prioritizing projects in Step 6. The assessment of the project economics is conducted using a Cost-Benefit Analysis (CBA) approach. Procedures for the economic assessment of projects are described in the Road Accident Reduction Program: Project Evaluation Handbook.

Step 6: Prioritize the Projects Whether or not a project delivers good value for money and is a cost-effective solution to the road safety problem is the major consideration when choosing between projects competing for funding. But other factors should also be taken into consideration. For example, if two projects have similar economic performance then it is reasonable to: •

prefer one that does not require land acquisition or resettlement;

•

prefer one that has less environmental impact; and

•

prefer one in a location with higher traffic volume since in most cases, implementing a road safety treatment will also produce benefits in terms of reduced congestion and fewer secondary accidents (accidents caused by the traffic disruption).

The prioritization process for road accident reduction projects uses a Multi-criteria Analysis (MCA) approach to calculate a multi-criteria score for each project. The multi-criteria score is a measure of the relative merit of a project taking into account a range of decision criteria, such as: •

the value that the project will deliver in terms of road safety benefits per peso of project cost;

•

its acceptability from a social and environmental perspective; and

•

its potential secondary benefits in terms of reduced congestion and reduced secondary accidents.

Sorting the projects from the highest scoring project to the lowest produces a prioritized list of projects. Projects near the top of the list are high priority projects. Projects that are selected for funding allocation should come from the group of highest scoring projects since these deliver the greatest road safety benefits.

Page 6


Procedures for establishing project priorities are described in the Road Accident Reduction Program: Project Evaluation Handbook.

Step 7: Deliver the Project The final step is to obtain budget allocation and release of funds, and implement the highest ranked projects. This Handbook does not cover the budget process for funding of road accident reduction projects, or the contracting and delivery of engineering works at hazardous locations.

Page 7


PART 3

PREPARATION OF ROAD ACCIDENT REDUCTION PROJECTS

This Part of the Handbook provides a step-by-step guide to the identification and investigation of hazardous locations, or blackspots, and the development of candidate projects to reduce the incidence and / or severity of road accidents at those locations. The project preparation phase comprises the first three steps in the project cycle: Step 1

Identify hazardous locations

Step 2

Investigate hazardous locations with an emphasis on those with the highest numbers of major accidents

Step 3

Develop a project of road safety improvements to reduce the incidence of accidents at each location investigated.

At the end of this stage of the project cycle, concept plans for infrastructure improvements to reduce the occurrence of accidents at hazardous locations will have been prepared and costed. Candidate projects will be submitted for evaluation in accordance with the processes and steps detailed in the Road Accident Reduction Program: Project Evaluation Handbook.

STEP 1 – Identify Hazardous Locations PREPARATION


Hazardous Locations


Potential Projects 3. FORMULATE candidate projects


EVALUATION

Candidate Projects

Eligible Projects 5. APPRAISE project economics

Project Scores 6. PRIORITIZE using multicriteria scores

DELIVERY

The first stage of the project cycle for the Road Accident Reduction Program is the identification of hazardous locations. The objective of this stage of the process is to establish which locations are the most hazardous, as indicated by accident statistics, as a precursor to progressing through the subsequent steps of project development and evaluation. By focusing resources on the most hazardous sites, the likelihood of achieving the most beneficial road safety outcomes for the community for each peso spent on blackspot projects will be maximized.

Prioritized List of Projects

7. DELIVER projects

To be eligible for consideration for inclusion in the Road Accident Reduction Program as a candidate blackspot project, a site must have a high frequency of accidents. The criteria in Table 3.1 should be met. Projects that do not meet the minimum criteria will be screened out at the project evaluation phase (refer Road Accident Reduction Program: Project Evaluation Handbook).

Table 3.1

Criteria for Identifying Blackspots

Location Type

Indicator of Potential Blackspot

Specific Location – Intersection or short midblock section (length<500m)

Average of 3 major accidents per year over the past 2 to 3 years

Road section

Average of 3 major accidents per year per kilometer of road length over the past 2 to 3 years

– Longer than 500 meters

The criteria are focused on major accidents, since fatal and serious injury accidents have the greatest impact on the community both in terms of economic and social costs.

Page 8


At this step in the project cycle, the aim is to draw on all sources of information and data to produce a list of hazardous locations that will be considered for treatment action. The primary source of information to establish the worst accident locations is TARAS. Other possible blackspot sites may be identified from other sources and these should be given due consideration. The process of identifying hazardous locations can be broken down into the following four steps: Step 1.1

Analyze accident data using TARAS to establish the locations with the worst accident history

Step 1.2

Review locations nominated from other sources

Step 1.3

Compile listings of worst accident locations

Step 1.4

Select sites for investigation

Each of these steps is described in detail in the following Sections, followed by a step-bystep guide to identifying hazardous locations.

Step 1.1

Analyze Accident Data

Accident data on the National Road Network is maintained in TARAS. Data on road accidents are collected and recorded in TARAS in a way that allows them to be analyzed within the system and produce a range of standard and user defined outputs in the form of reports, charts and maps that are suited to specific needs. Minimal knowledge of the TARAS program is required to produce many of the standard outputs. For detailed information on the use of TARAS, readers should refer to the TARAS Users Manual. To establish the most hazardous locations, a report that lists the worst accident sites should be produced from TARAS. The report must cover a period of at least two years, preferably three, to be consistent with the criteria for identifying blackspots shown in Table 3.11. The standard TARAS Rank report for worst accident sites will produce a list of all sites in the designated area that meet the minimum accident criteria. Reports can be produced for each DPWH Region and/or District as required. They can also be produced at a National, Province or Local Government level. Maps showing hazardous locations can also be produced. These are useful to gain a visual appreciation of the distribution of blackspot locations. They also will show where clusters of blackspot locations exist along a particular road or within a confined area. These may need to be investigated as a group, rather than individually, to determine if there are common factors that are contributing to the accidents. Samples of typical reports and maps from TARAS are included in Appendices A, B and C.

1

In the early phase after implementation of TARAS only limited data may be available. During this phase at least one complete year of data would be desirable.

Page 9


Step 1.2

Review Locations Nominated from Other Sources

Possible blackspots can also be identified from a number of other sources, such as Regional or District DPWH engineers, community members and local government officials. The local knowledge of hazardous locations from such sources often provides valuable additional information, particularly about the cause of accidents. Sites nominated from such sources should be checked against the reports of worst accident locations produced from TARAS in Step 1.1. If the site is included, proceed to the next step, otherwise the accident history of the nominated location should be extracted from TARAS. If the recorded accident history does not meet the minimum criteria for identifying blackspots, the location should not be included on the final list of worst accident locations unless there is an alternative source of reliable data on major accidents at the site (for example police records that have not been recorded in TARAS). Sites that do not meet the blackspot criteria could be reviewed under the Road Safety Audit Program and eventually included for treatment in the Accident Prevention Program.

Step 1.3

Compile Listings of Worst Accident Locations

Having identified blackspot locations in Steps 1.1 and 1.2, the next task is to compile final listings, from which sites will be selected for detailed investigation. Separate lists should be produced for: •

specific locations (intersections and short mid-block sections less than 500 meters in length); and

•

road sections (longer than 500 meters).

Locations on the lists should be ranked based on average accident rates (i.e. major accidents / year or major accidents / km / year as appropriate). This will allow accident rates to be readily checked for compliance with the criteria for identifying blackspots. Checking compliance at this stage will minimize the possibility of wasting resources on investigation and the development of a project that would be screened out during the evaluation phase. Preparation of the lists using an electronic spreadsheet, such as Microsoft® Excel®, can be useful as the data can be readily sorted. A copy of an Accident Blackspots Ranking spreadsheet that can be used for recording this information is in Appendix J. This spreadsheet also includes columns for addition of data and the formulas required for the Project Evaluation phase of the project cycle. The lists of worst accident locations should be updated annually to ensure they reflect the most recent accident data and that resources continue to be focused on the most hazardous locations.

Step 1.4

Select Sites for Investigation

Priority for site investigation and subsequent steps in the project cycle is generally given to those locations with the highest accident rates. Sites at which there have been treatment works recently implemented (say, within the past two years) either under the Road Accident Reduction Program or another road infrastructure program, should be filtered out and not investigated unless accident records show that the previous treatment has not improved road safety.

Page 10


Due consideration should be given to proceeding to the investigation step for sites where there have been significant safety concerns raised by the community or local officials even though the accident rate may be lower than would normally warrant investigation. The actual number of locations to be investigated will depend upon the resources available to undertake the investigations and subsequent project development activities as well as the level of funding available to implement accident reduction projects.

Step-by-Step Guide Table 3.2 provides a step-by-step guide to the identification of hazardous locations.

Page 11


Table 3.2

Step-by-step Guide to Identification of Hazardous Locations

Step

Explanation

Step 1.1

Obtain reports and maps of worst accident locations from TARAS for the designated area.

Analyze Accident Data

Reports and maps should be produced for at least the most recent two, preferably three, years for which complete accident data is available. Maps will indicate where accident sites are clustered in an area or along a length of road.

Step 1.2 Review Locations Nominated from Other Sources

Review locations nominated from other sources (e.g. Regional or District DPWH engineers, community, local government officials). Is the site included in the TARAS report of worst accident locations? If yes, proceed to Step 1.3 If no, extract accident data for the site from TARAS and/or check alternative reliable source of accident data Does the accident history meet the criteria for identifying blackspots (Table 2.1)? If yes, include in listings of worst sites. If no, do not consider the site any further for the Road Accident Reduction Program.

Step 1.3 Compile Listings of Worst Accident Locations

Step 1.4 Select Sites for Investigation

Compile lists, ranked by average accident rate based on the information from Steps 1.1 and 1.2 for specific locations (intersections and mid-block lengths less than 500 meters) and road sections. Do all locations listed conform to the minimum accident criteria for identifying blackspots? If yes, proceed to Step 1.4 If no, remove non-conforming locations from the lists then proceed to Step 1.4

From the listings of worst accident locations, select the sites to be investigated taking into consideration the following factors: •

Give priority to sites with the highest number of major accidents

•

Consider sites where there is a high level of community concern

•

Impacts of recently completed treatment works

•

Other planned road infrastructure projects that may affect a site

•

Resources available to undertake investigations and the development of projects

•

Funding available to implement projects

Page 12


STEP 2 – Investigate Hazardous Locations PREPARATION

Hazardous Locations




Candidate Projects



DELIVERY

The investigation of hazardous locations requires a systematic and logical step-by-step approach and an understanding of the nature of road accidents.


EVALUATION

Step 1 of the project cycle established a list of the most hazardous locations for which investigations would be conducted. The objectives of the investigation of a hazardous location are to identify the predominant accident types and patterns and by the analysis of reported accidents and examination of the site, reach conclusions regarding the factors contributing to accidents.


7. DELIVER projects

The road traffic system comprises three elements – the human, the vehicle and the road. The interaction between these elements is complex and the road user, whether a driver, rider or pedestrian, is required to continually process information and make decisions. The safe operation of the road system requires these decisions to be correct. Good road and traffic engineering can assist by ensuring that the road user is presented with a road system that, as far as practicable, is predictable, minimizes the need for complex decisions by guiding, warning and reducing the number of potential conflicts and is forgiving so that the consequences are not severe if mistakes are made. Figure 3.1 shows the typical mix of human, vehicle and road environment factors involved in road accidents. The diagram shows for example that around 95% of accidents involve an error by the road user, whilst 24% involve a combination of human and road environment factors.

H u m a n fa c to rs (9 5 % ) Road e n v iro n m e n t fa c to rs (2 8 % )

24% 67%

V e h ic le fa c to rs (8 % )

Figure 3.1 Contributing Factors in Road Accidents

While the road environment is a contributing factor in a little over one quarter of road accidents, improved engineering of the road and roadside can have an impact on a larger proportion of accidents by modifying driver behavior or by ensuring that the severity of the outcome of an accident is minimized. For example, if a driver strays off path on a country road when talking on a cell phone, he / she has more chance of regaining control of the vehicle if the shoulders on the road are paved. In addition, the outcome of a resulting accident is likely to be less severe if there are no hazardous objects (poles, trees etc) close to the road.

Page 13


The process of investigating a hazardous location can be broken down into the following five steps: Step 2.1

Collect the accident data relevant to the hazardous location

Step 2.2

Presentation of the accident data in a format which facilitates analysis

Step 2.3

Analyze the accident data to establish accident patterns and common characteristics

Step 2.4

Inspect the accident site

Step 2.5

Review the information and formulate conclusions regarding causes and possible solutions

Each of these steps is described below, followed by a step-by-step guide to the investigation of hazardous locations.

Step 2.1

Collect the Accident Data

The first step of the hazardous location investigation phase is to collect all the accident data and information relevant to the site being investigated. The primary source of accident data is TARAS. TARAS Data A range of standard and customized outputs is available from TARAS for both intersections and mid-block sections of road. The most commonly used and useful TARAS output to assist with the investigation of a hazardous location is the Listing report. A sample is attached as Appendix B. This report will generally provide most of the accident data that are required for the investigation phase. For each recorded accident, the report includes information on: •

date, day and time of occurrence;

•

overall accident severity (fatal, serious injury, minor injury) as well as the injury level of each person involved;

•

number, gender and age of the people involved;

•

accident type, including the Traffic Accident Description (TAD) (refer to Step 2.2 for explanation of TAD);

•

light (day, night etc) and weather conditions (wet, dry etc);

•

vehicles involved and direction of travel at the time of the accident;

•

road users involved (driver, passenger, bicyclist etc); and

•

location details, including type of traffic control (e.g. traffic signals), type of road surface etc.

The period over which accidents are to be included in the investigation should be as long as possible so that accident patterns and trends can be established. A minimum of two years of accident data is desirable and a maximum of five years should be adopted. Accidents that occurred more than five years ago are likely to have limited relevance to current conditions.

Page 14


In the period immediately following the implementation of TARAS, limited accident data may be available. During this time at least one year of data would be desirable. It should be kept in mind that the evaluation of a blackspot project that is developed as a consequence of an investigation will generally be assessed using the average accident rate over the most recent two or three years. Accident histograms or bar charts can also be produced from TARAS. These can be used to highlight particular characteristics and accident patterns at a hazardous location. Common factors that can be displayed on histograms include; •

TADs;

•

collision types;

•

time of day or day of the week;

•

vehicle types;

•

weather condition; and

•

light condition.

A sample of a histogram in the form of a TARAS Summary report is attached as Appendix C. Histograms alone rarely provide sufficient information to allow accident patterns to be explained. However, they can provide a strong visual representation of particular characteristics of accidents at a hazardous location. Traffic Accident Report (TAR) Forms A TAR form is filled out by the police following an accident. The TAR is the source of the information about an accident that is housed in TARAS. During the course of a hazardous location investigation most of the information pertaining to each accident can be accessed through TARAS without the need to see the TAR forms. However, for many, if not most investigations, it is desirable to obtain a copy of each of the accident forms relating to the hazardous location as they can aid in developing a better understanding of the causes of the accidents that are being investigated. Comments provided by the attending police officer and the sketch diagram of the accident that is provided on the form can be particularly informative. A sample of a completed TAR form is provided in Appendix D.

Step 2.2

Presentation of the Accident Data

The reports and histograms produced from TARAS provide the basic forms of presentation of accident data. However, translation of the available information into alternative formats can greatly assist the process of analyzing the data, identifying accident patterns and reaching conclusions about likely contributing factors. Traffic accident data recording and reports use Traffic Accident Description (TAD) codes to provide information about the accident. Traffic Accident Description (TAD) Codes A TAD code is a number that is assigned to identify particular accident types. For example, a collision between a left turning vehicle at an intersection and another vehicle traveling straight through from the opposing direction has a TAD code of 122. The chart showing all TAD codes is included as Appendix E. Note that each column of the chart corresponds with a particular grouping of accident types. For example, all accident types that involve overtaking movements are in the same column and are part of the 150 series of TAD codes. This method of coding and classifying of accidents facilitates extraction of data from TARAS and the accident analysis process.

Page 15


Collision Diagram A collision diagram is a diagrammatic representation of the accidents that have occurred at an intersection or along a section of road. It provides a visual summary of the accident patterns, overlaying an outline sketch that is representative of the intersection or section of road. A typical collision diagram is shown in Figure 3.2.

Figure 3.2:

Collision diagrams are very effective in highlighting the predominant accident patterns at a particular site. Collision diagrams can be prepared using information contained in a TARAS accident listing, however, greater accuracy is assured if the TARs are used.

Page 16


The main features of a collision diagram are: •

each accident is represented by arrow(s) and/or symbols for each road user or object involved in the accident;

•

arrows indicate the direction of travel or the movement being made at the time of the collision. Generally, fatal, serious injury and minor injury accidents are represented by a closed circle, an open circle and short bar respectively, at the point of contact;

•

the same accident types are clustered; and

•

accident details, including date, time, weather condition and light condition, may be included as labels (particularly if the diagram is relatively simple and uncluttered).

TARAS Summary Report A TARAS Summary Report can assist in the presentation of accident data and in the analysis of traffic accident attributes and patterns. These can be used to show a trend in collision type (TAD codes), or other information relevant to the accident problems such as accidents in the wet, accidents at night or accidents involving specific types of road users. An example of a TARAS Summary Report is in Appendix C. Histogram / Chart A histogram or chart of traffic accident factors using a spreadsheet can also assist in the identification of trends and in the presentation of data. These may show a pattern in accident types or other data relevant to the accident problem. Accident Factor Chart An accident factor chart can be used to present accident data in a tabular format to assist with analysis and identification of common factors. This type of analysis may be desirable where manual examination of data is needed rather than the TARAS Summary Report. Items of data in the tabulation would generally include TAD codes, accident severity, day of week, time of day, light conditions, road surface conditions and the direction of vehicles or a sketch of the accident. Sample accident factor charts (completed and blank) are in Appendix F.

Step 2.3

Analyze the Accident Data

Analysis of the accident data is the first step towards diagnosing the accident problem at the location that is being investigated. The objective of this step is to: •

identify the predominant accident types;

•

establish common factors and patterns in accident data; and

•

formulate preliminary ideas about the road environment factors that may be contributing to accidents.

The data collected and presented in Steps 2.1 and 2.2 provide the basis for a desktop analysis, although the investigator may have pre-existing knowledge of the site which will add value. Careful and systematic examination of accident listings, histograms, collision diagrams and accident factor charts is required to identify the predominant accident types and patterns and establish possible links to the road environment. Examination of a site plan, if available, would also provide further understanding of the site.

Page 17


It is not unusual to have two or more common accident types at a particular location. Conversely, at some locations the accident types might be quite diverse and there may not be a dominant type. Under such circumstances it becomes more important to systematically and logically examine the data to determine any common factors and patterns, and relate these to site conditions and driver behavior. At this stage some consideration of possible treatment options would be desirable so that implications of various treatments can be considered during the next step in the process when the site is inspected. However, at this point it is important not to jump to conclusions, as subsequent steps in the process are critical to a full understanding of the situation and the successful outcome of the project preparation process.

Step 2.4

Inspect the Accident Site

The next step is to inspect the intersection or section of road that is being investigated. The objectives of the site inspection are to: •

become familiar with the location that is being investigated;

•

gather information on road and roadside features and conditions that may be contributing or relevant to the accident types and patterns; and

•

observe traffic operation and road user behavior;

When conducting a site inspection it is important to remember that a road accident is a rare event. While many thousands of road users can safety pass through an intersection or along a section of road without incident, occasionally an accident occurs when someone fails to cope with the road environment. The reasons for this breakdown are not always obvious. Consequently, the site inspection needs to be thorough and systematic so that any possible road or roadside features that may have contributed to accidents are identified. Prior to the inspection, obtain a copy of a plan of the site, if available. Examine the plan, keeping in mind the knowledge gained from the accident analysis in the previous step, and note any features that may require attention during the site inspection. However, continue to keep an open mind on possible causes and treatment options. Another source of site information that may be useful is the Road and Bridge Information Applications (RBIA) database. Some important principles regarding site inspections are: •

The site should be driven and walked to gain the greatest possible appreciation for the road and roadside environment from the relevant road user’s perspective. Where appropriate, it may be necessary to ride by bicycle or motorcycle;

•

The timing of an inspection may need to coincide with the predominant time that accidents have occurred, for example a specific time of day or night;

•

The inspection should extend beyond the immediate vicinity of the accident location to ensure that all possible contributing factors are accounted for; and

•

Take plenty of photographs of the site. These are useful for further review in the office or when considering the implementation of a particular treatment. A video recording can also be useful for further consideration.

Page 18


A site inspection may need to consider the following factors: •

Road and traffic environment, including the topography and surrounding land use

•

Type of traffic control (no control, give way or stop signs, traffic signals, roundabout)

•

Pedestrian facilities

•

Visibility for drivers – consider driving position for various types of vehicles

•

Visibility for pedestrians

•

Standards of existing road layout (horizontal and vertical geometry)

•

Adequacy of existing warning or regulatory signs

•

Condition of the road surface

•

Driving behaviour

•

Speed of traffic

•

Traffic volumes and mix of vehicles

•

Type and number of other road users – pedestrians, cyclists etc

•

Night time use of the site

•

Conditions in the wet

•

Conditions in fog or when the sun is low in the sky

The site visit should also be used to consider the implications relating to the choice of improvement options and the implications related to construction of the works. A record of the site inspection with relevant notes should be kept. An example of a typical format, is included as Appendix G.

Step 2.5

Review the Information and Formulate Conclusions

The final step of the investigation stage is to review all the information gathered about the hazardous location and formulate conclusions regarding the causes of accidents and the treatment proposal that is likely to be the most effective in improving safety at the location. The outcomes of the accident analysis and the information gathered from the site inspection need to be closely examined to determine if there are road or roadside improvements that could be implemented to reduce the accident risk or whether there are behavioral factors that may need to be addressed through enforcement or community education. In some cases a combination may be appropriate. It should be remembered that although the causes of accidents at a location may be related to behavior, engineering solutions may also be appropriate. For example, at an intersection where the speed is a major cause of accidents, the construction of a roundabout (rotonda) may be a good solution, as it will force a reduction in vehicle speeds through the intersection. If necessary, further information about the hazardous location should be sought at this stage. The police, local government engineers and the community, particularly those living or working near the site, can often provide valuable local knowledge that will add value and assist in reaching a conclusion about the cause of accidents.

Step-by-Step Guide Table 3.3 provides a step-by-step guide to the investigation of hazardous locations.

Page 19


Table 3.3

Step-by-step Guide to the Investigation of Hazardous Locations

Step

Explanation

Step 2.1

Collect all accident data relevant to the hazardous location to be investigated.

Collect the Accident Data

Obtain accident listings and, where necessary, histograms from TARAS. Obtain copies of all Traffic Accident Reports from the DPWH regional office.

Step 2.2 Presentation of the Accident Data

Present the accident data in a format that is best suited for analysis purposes using some or all of the following: TARAS accident listings TARAS histograms Collision diagram Accident factor chart Spreadsheet analysis

Step 2.3 Analyze the Accident Data

Carefully and systematically examine the accident data to: Identify predominant accident types. Establish common factors and patterns. Formulate preliminary ideas about the road environment factors that may be contributing to accidents.

Step 2.4 Inspect the Accident Site

Inspect the hazardous location to become familiar with the site, gather information on relevant road and roadside features, and observe traffic operation and road user behavior. Drive, walk, ride through the site, as appropriate. Inspect at time that coincides with predominant time of occurrence of accidents. Extend the inspection beyond the immediate vicinity of the accident site. Take photographs and, if necessary, video recording. Keep a record of the site inspection (refer Appendix G)

Step 2.5 Review the Information & Formulate Conclusions

Review outcome of accident analysis and information from site inspection, seek addition information as required and formulate conclusions regarding the treatment proposal that is most likely to be effective.

Page 20


STEP 3 – Formulate Candidate Projects PREPARATION


Hazardous Locations




EVALUATION

Candidate Projects



DELIVERY

The final step of the project preparation phase is to formulate a treatment proposal. The objective of this step is to develop a blackspot project proposal comprising engineering measures that will effectively address the predominant accident types at the hazardous location. In some cases, recommendations relating to enforcement and / or community education campaigns may be appropriate to address matters relating to driver behavior.


7. DELIVER projects

As previously mentioned, the cause of accidents is complex. They occur when the road user fails to cope with the road environment. But a road accident is the end result of a chain of events, most of which the road safety engineer has no control over. The objective of treating hazardous locations with engineering measures is to break the chain of events that has lead to accidents in the past. It is rare that the investigation carried out in Step 2 will point to a single cause of accidents at a blackspot location. Accordingly, there is generally a number of different remedial safety treatments that could be applied either individually or in combination. In developing the treatment proposal for a blackspot, measures that have proven to be successful in reducing the incidence of accidents in similar circumstances should be applied. The process of formulating a candidate project can be broken down into 5 steps: Step 3.1

Identify treatment options that address the predominant accident types

Step 3.2

Develop a preliminary treatment proposal that will maximize expected benefits

Step 3.3

Review site constraints and modify the treatment proposal accordingly

Step 3.4

Prepare a concept design plan

Step 3.5

Prepare a cost estimate based on the concept design

Step 3.6

Write a hazardous location report

Note that Steps 3.2 to 3.5 may be iterative, that is, it may be necessary to review the outcome of earlier steps if factors identified in subsequent steps make this necessary. For example, when preparing a concept plan it is discovered that a satisfactory design cannot be achieved without land acquisition and resettlement, which had not been expected to be necessary, there may be a need to return to Step 3.2 and review the treatment proposal. Similarly, if an expensive treatment is not viable, a lower cost option may need to be recommended. Each of these steps is described below, followed by a step-by-step guide to the formulation of candidate projects.

Step 3.1

Identify Treatment Options

The objective of this first step in the development of a treatment proposal is to identify the engineering measures that would be most likely to be effective in reducing the incidence or severity of accidents at the blackspot location that was investigated in Step 2 of the project preparation phase. As mentioned previously, it is likely that the final treatment proposal will comprise a number of measures. At this stage, all possible treatment options need to be identified. In subsequent steps the options will be examined and an overall treatment proposal will be developed.

Page 21


The choice of treatment also needs to take into consideration the appropriateness of a treatment in the context of the road environment and road network at the location. For example, traffic signals or street lighting may not be appropriate in a rural environment. Table 3.4 provides guidance on the types of countermeasures that are applicable to some of the common accident types at intersections and on road sections. Whilst the table is quite comprehensive, it by no means shows the complete range of treatments and possible approaches to improving safety at blackspots. Treatments utilizing new technology are continually being developed and tested. Table 3.4

Guide to Countermeasure Treatments

Accident Type

Treatment Options

a) Countermeasures for Intersection Accidents Right angle / cross traffic

Left turn with opposing through traffic

•

Clear obstructions if sight distance is inadequate.

•

At a stop or give way controlled intersection where the accidents are due to vehicles failing to stop on the controlled approach (i.e. overshooting), install / improve advance warning signs, advance direction signs, median island, more conspicuous or duplicate give way or stop signs; repaint / install center lines and holding lines.

•

Install traffic signals in an urban environment if low cost treatments will not be effective (i.e. gap acceptance problems) and if traffic volumes are moderate to high.

•

Install a roundabout (rotonda) if traffic volumes are moderate to high and side road carries significant traffic.

•

Realign minor road approaches to create offset T intersections if low cost treatments are not effective and traffic volumes are low.

•

Prevent the cross movement on the minor road by closing the median (on a divided road) or installation of traffic islands on the minor road approaches to allow right in and right out only (note: these treatments will also affect turning movements in addition to cross traffic movements).

•

Improve visibility of existing traffic signals, if necessary by removal of obstructions, installation of additional signal lights (may include overhead lights); provision of traffic signal warning signs.

•

Adjust traffic signals to increase yellow and / or all red periods.

•

Clear obstruction if sight distance to opposing through traffic is inadequate.

•

Modify intersection geometry if visibility for left turn vehicles is obstructed by left turn traffic from the opposite direction.

•

If intersection is signalized, provide fully controlled left turn phase (i.e. green, yellow and red left turn arrows).

•

Provide exclusive left turn lane.

•

Construct roundabout (rotonda) if low cost options are not effective and traffic volumes are moderate to high.

•

Ban the left turn movement if turn volume is low and there are alternative routes.

Page 22


Accident Type

Left turn or right turn / rear end

Straight ahead / rear end

Pedestrian

Night time (all accident types)

Wet weather (all accident types)

Treatment Options

•

Provide auxiliary left or right turn lane as appropriate.

•

Extend existing or provide additional auxiliary left / right turn lane if length is inadequate.

•

Ban the left turn / right turn movement if the turn volume is low and there are alternative routes.

•

Install additional signal lights (including consideration of overhead lights) or clear obstructions if visibility of traffic signals is inadequate.

•

Disallow right turn on red at a signalized intersection, if a contributing factor.

•

Realign right turn slip lane to provide high entry angle (60° - 70°).

•

Install additional signal lights (including consideration of overhead lights) or clear obstructions if visibility of traffic signals is inadequate.

•

Clear obstructions or install advance warning signs (including consideration of illuminated signs linked to traffic signals to advise drivers to prepare to stop) if the sight distance to the back of queued traffic is inadequate.

•

Provide / extend auxiliary left or right turn lane if accidents are due to queuing by uninvolved turning vehicles.

•

Provide pedestrian crossings and / or pedestrian signal lights at signalized intersections.

•

Install “give way to pedestrians” signs at existing crossings at signalized intersections.

•

Install pedestrian islands to simplify the task of crossing the road.

•

Extend curbs into the roadway to simplify the task of crossing the road and reduce the crossing distance.

•

Install fencing to prevent pedestrians from crossing at hazardous locations and direct them to safer crossing points.

•

Construct sidewalk if none exists.

•

Install warning signs.

•

Disallow right turn on red at signalized intersection.

•

Install / improve line marking (lane lines, stop bars, centerlines etc.), reflective pavement studs.

•

Install / improve signages (warning, direction and regulatory).

•

Install / improve street lighting if in an urban area.

•

Install / improve pavement markings (lane lines, stop lines, centerline), and reflective pavement studs.

•


•

Improve skid resistance of road pavement.

•

Improve drainage of road pavement.

Page 23


Accident Type

Treatment Options

b) Countermeasures for Accidents on Road Sections Run-off-road

Hit roadside object (including bridge)

Head on

•

Install / improve line marking (including centerlines and / or edge lines), reflective pavement studs.

•

Install chevron alignment signs, curve warning signs with advisory speed.

•

Repair / maintain gravel shoulders to avoid drop off at edge of road pavement and provide smooth shoulders.

•

Pave gravel shoulders and provide edge lines (consider need for profiled edge lines).

•

Improve alignment of low standard curves and / or superelevation and / or pavement shape.

•

Widen traffic lanes if narrow (particularly on low radius curves).

•

Flatten steep cut or fill slopes (make 1 in 4 or flatter) and ensure that they are smooth and free of hazards within the clear zone (refer also to “hit roadside object” in this table).

•

Install safety barriers where cut or fill slopes are steep and cannot be flattened.

•

Consider all treatment options listed for run-off-road accidents.

•

Remove the hazardous roadside object or relocate it to a low risk location (usually beyond the clear zone).

•

Replace rigid lighting poles or sign posts with frangible poles / posts.

•

Where it is not possible to remove or relocate a hazardous roadside object, install a safety barrier or impact attenuator.

•

Install guardrail (fastened to bridge end post) on the bridge approach to provide protection.

•

Upgrade / replace hazardous bridge railing.

•

Provide / improve centerline marking, including installation / extension of barrier lines and the installation of reflective pavement studs.

•

Repair / maintain gravel shoulders to avoid drop off at edge of road pavement and provide smooth shoulders or paved shoulders if head on accidents are the result of vehicles losing control on the shoulders.

•

Improve alignment of low standard curves and / or superelevation if head on accidents are occurring on a curve.

•

Widen traffic lanes if inadequate.

•

Increase separation between opposing traffic flows by construction of a median (could be raised or painted).

•

Install safety barriers to separate opposing traffic flows.

•

Construct overtaking lane.

Page 24


Accident Type

Hit parked / stopped vehicle

Pedestrian

Night time (all accident types)

Wet weather (all accident types)

Step 3.2

Treatment Options

•

Prohibit parking - either full time or part time (e.g. during peak traffic periods only if accidents occurring during these times).

•

Provide indented parking bays or increase the separation between the parking lane and the through traffic lanes.

•

Relocate bus / jeepney stop or provide indented bays.

•

Install mid-block pedestrian operated signals.

•

Install zebra pedestrian crossing if on low speed road.

•

Install pedestrian islands and / or extend curbs into roadway to simplify the task of crossing the road and reduce the crossing distance.

•

Install fencing to prevent pedestrians from crossing at hazardous locations and direct them to safer crossing points.

•

Construct sidewalk if none exists or curb to separate vehicles and pedestrians.

•

Provide wider shoulder to increase separation between vehicles and pedestrians.

•

Install warning signs.

•

Install / improve line marking (centerlines and / or edge lines), reflective pavement studs.

•


•

Install / improve street lighting if in an urban area.

•

Install / improve line marking, reflective pavement studs.

•


•

Improve skid resistance of road pavement.

•

Improve drainage of road pavement.

Develop a Preliminary Treatment Proposal

Having identified the range of possible engineering treatments that should be considered to target the specific accident types that have occurred at the blackspot under investigation, the next step is to develop a preliminary treatment proposal comprising a package of measures that are expected to achieve the greatest reduction in the frequency of accidents. However, the benefits need to be achievable in a cost effective manner. The cost effectiveness of candidate projects will be determined in the evaluation phase of the project cycle. The treatment package could include recommendations regarding enforcement and / or community education initiatives, particularly if the investigation indicates that engineering treatments are not likely to have a significant impact at a particular site. Such recommendations, however, are the responsibility of the enforcement or community agencies to consider and implement and therefore do not form part of the project to be evaluated.

Page 25


It is strongly recommended that accident investigators have a good working knowledge of the project evaluation process (Steps 4, 5 and 6 of the project cycle), which is set out in the Road Accident Reduction Program: Project Evaluation Handbook. An understanding of the methodology and the parameters used to conduct an economic evaluation and rank projects in order of priority for consideration of funding will maximize the chances of producing candidate projects during the project preparation phase that will be cost effective and more likely to be funded. More particularly, to develop a treatment proposal that is to be effective, knowledge of the likely reductions in accident rates for different treatment types is required. Table 3.5 shows accident reduction factors (percentage reduction in the number of accidents) for a range of standard treatment types. These accident reduction factors are derived from international experience and have been cross-checked against available information on the outcomes of past road safety treatment works in the Philippines. The table also includes the typical treatment life for each treatment type, which is the period of time road safety benefits are expected to be achieved. The table indicates that the benefits and cost effectiveness of low cost treatments such as improved signages, linemarking and reflective pavement studs compared to geometric improvements, which are usually significantly more costly, are offset by the fact that their treatment life is shorter. The parameters shown in Table 3.5 are used in the project evaluation phase.

Page 26


Table 3.5

Treatment Types and Accident Reduction Factors

Treatment Type Signal installation Fully control left turns (green, yellow & red left turn arrows) Improve traffic signal visibility – remove obstructions, install additional lights (including overhead) Roundabout (Rotonda) Geometric improvements, channelization islands (including to restrict cross traffic movements), auxiliary left turn lane Auxiliary right turn lane, realign right turn slip lane Extend left / right turn lane Prohibit left turns Improve sight distance – clear obstructions, modify geometry to improve visibility for turning vehicles etc Signages – warning, advisory & regulatory signs Pavement markings - centerlines, edge lines (including profiled edge lines) Reflective pavement studs (RPS) Road re-alignment – on curves and at intersections to create offset T Improve superelevation on curves Improve / provide gravel shoulders Pave shoulders Widen traffic lanes Remove roadside hazards, install frangible poles Road safety barriers – guards rails (including at bridge end posts), wire rope & concrete, upgrade bridge rails Flatten fill / cut slopes Improve skid resistance, road pavement drainage Indented parking, ban parking, indented bus / jeepney stop, relocate bus / jeepney stop Median strip Passing lane (overtaking) Pedestrian island, construct sidewalk, curb extension, curb construction or widen shoulders to separate vehicles and pedestrians Install pedestrian operated signals Install zebra pedestrian crossing (low speed roads) Disallow right turn on red Pedestrian fencing Street lighting

Accident Reduction Factor (%)*

Typical Treatment Life (Years)

40 20

20 20

10

20

75

20

35

20

15 10 10

20 20 10

15

20

25

10

25

10

15

10

50

20

20 10 30 10 15

20 10 20 20 20

20

15

10 15

20 10

10

20

40 20

20 20

35

20

25 15 10 15 25

20 10 10 10 10

*Note: Accident Reduction Factor and Typical Treatment Life values are NOT ADDITIVE. The highest value is used if multiple treatments are proposed.

Page 27


The preliminary treatment proposal should target as many of the accidents at the site as possible although the primary objective is to address the predominant accident types. Optional proposals need to be considered, particularly where treatment costs are likely to be high. Take, for example, a blackspot site where there has been a history of run-off-road accidents on a low radius curve. Option 1 is to realign the curve and improve the superelevation. This treatment would involve significant costs, particularly if land acquisition is required. Option 2 is to paint edge lines and install warning signs and chevron alignment signs. Option 2 would be less costly but would have a lower accident reduction factor (25% compared to 50% from Table 3.5) and a shorter treatment life (10 years compared to 20 years). Ultimately, the evaluation process would determine which option is more cost effective. When developing the preliminary treatment proposal, consideration may also need to be given to the volume of traffic and mix of vehicles at the site. At an intersection, this would generally require maximum hourly volume data for turning movements (left turning, right turning and through traffic) using each intersection approach, particularly during peak periods. If the intersection layout were to be changed (e.g. for provision of traffic signals, roundabout or addition of turn lanes etc.), this traffic volume information would be used for capacity analyses during the peak hourly traffic flows. A turning movement count may need to be arranged if the peak hour traffic volume data is not available or cannot be readily estimated.

Step 3.3

Review Site Constraints and Modify Treatment Proposal

Prior to proceeding to the preliminary design stage, a review of the blackspot site should be conducted to ensure that the proposed treatment proposal and options are practical and achievable. The objective of this step is to ensure the appropriateness of the proposed treatments in the context of the road environment and the road network. This may require another site inspection. The review should identify any properties that may be affected and if resettlement of persons living on the site may be necessary. Property acquisition and resettlement of owners or squatters can add substantially to the human and social impact of a project and result in high project delivery risks in terms of cost and time required to resolve land issues. Where appropriate, changes to the preliminary treatment proposal should be made to minimize or avoid land acquisition and resettlement if possible. Possible environmental impacts also need to be considered and minimized. Significant impacts might include major earthworks, changes to drainage patterns and disturbance of native forests or wildlife. Environmental impacts are unavoidable in many road projects, but: •

the impacts should be a small as possible;

•

contained within the project site as far as practicable; and

•

remedial works to reinstate the site to good environmental condition should be included in the project cost estimate.

Candidate projects that have significant acquisition, resettlement or environmental impacts and / or costs are likely to be filtered out during the evaluation phase (refer Road Accident Reduction Program: Project Evaluation Handbook). Cross-checking of the treatment proposal against the outcome of the accident analysis, to confirm that the major accident types and as many other accidents as practical have been addressed, should also be conducted at this stage.

Page 28


Step 3.4

Prepare Concept Design Plan

The objective of this step is to produce concept or preliminary layout plans to a sufficient level of detail to demonstrate that the treatment proposal is practical and able to be implemented, to display its main features and impacts, and to provide a basis for the preparation of a preliminary cost estimate. Minor projects such as those involving pavement marking and signage works only, or minor changes to traffic signal hardware (e.g. the installation of a traffic signal pole with overhead lights) may not require concept plans if a clear description of the scope of the proposed works will be sufficient. The concept plan is to be a two dimensional plan, which shows the following: •

Existing and proposed property boundaries and nearby buildings;

•

Existing and proposed curb lines, traffic islands and / or edges of paved roadway and shoulders;

•

Proposed lane widths and other critical dimensions;

•

Existing and proposed traffic signal poles and signage; and

•

Location of utilities.

While a two dimensional plan only is required at this stage, some design in the vertical dimension may be required to confirm the practicality of the proposed treatment and assist with the preparation of a cost estimate. For example if level differences will require the construction of a retaining wall to confine earthworks, some detail will be required to establish the extent of the work so that costs can be estimated with a reasonable level of confidence. As the design proceeds, it may be necessary to modify the treatment proposal to account for any issues that arise.

Step 3.5

Prepare Cost Estimate

A preliminary cost estimate, based on the concept plan is to be prepared. The preliminary estimate would generally be itemized as follows: •

Project development, survey and design;

•

Land acquisition & resettlement;

•

Alterations to utilities;

•

Roadworks;

•

Remedial environmental works;

•

Signages and pavement markings;

•

Street lighting;

•

Traffic signal installation / alterations;

•

Contingency; and

•

Project management.

Page 29


A typical preliminary cost estimate is included as Appendix H. Blackspot projects are typically small in comparison with other road infrastructure projects and the changes in ongoing maintenance and operating costs associated with road safety projects are not significant. Accordingly, they can be ignored in the economic evaluation process and there is no requirement to estimate such costs.

Step 3.6

Write an Accident Blackspot Report

The final step of the project preparation phase is to write an accident blackspot report. The objective of this step is to document the outcome of the accident investigation and provide details of the proposed treatment proposal. The report is to be submitted for evaluation of the project and ranking for consideration for inclusion in the Blackspot Program. The report should include the following: •

Location details, including Region, District, road name(s) and locality;

•

The investigation person or team;

•

Description of existing conditions, including daily traffic volumes and composition

•

Photographs of the site;

•

Details of reported accidents, including TARAS listing;

•

Outcome of the accident analysis, identifying predominant accident types and patterns;

•

Conclusions regarding causal factors, particularly site conditions and/or driver behavior;

•

Treatment options considered;

•

The recommended treatment proposal;

•

Details of project scope, including identification of land acquisition and resettlement, and environmental impacts;

•

A concept plan (may not be required for pavement marking and signage projects);

•

Preliminary cost estimate.

A typical report format is included as Appendix I.

Step-by-Step Guide Table 3.6 provides a step-by-step guide to the formulation of candidate projects.

Page 30


Table 3.6

Step-by-step Guide to the Formulation of Candidate Projects

Step

Explanation

Step 3.1

Identify all possible treatment options that are applicable to the accident types and patterns identified in Step 2.

Identify Treatment Options Step 3.2 Develop Preliminary Treatment Proposal

Refer to Table 3.4 – Guide to Countermeasure Treatments

Develop a preliminary treatment proposal that will effectively target the predominant accident types and as many of the other accidents as practicable. Use Table 3.5 as a guide to the effectiveness of treatment types. Working knowledge of the project evaluation process is recommended. Develop optional proposals as necessary.

Step 3.3 Review Site Constraints and Modify Preliminary Proposal Step 3.4 Prepare Concept Design Plan

Review the site, including another inspection if needed, to ensure appropriateness of the proposed treatments in the context of the road environment and road network. Cross-check the preliminary treatment proposal to confirm that it addresses the predominant accident types. Amend the treatment proposal as necessary. Prepare a concept design which shows: Existing / proposed property boundaries and buildings; Existing / proposed curb lines, traffic islands and / or edges of paved roadway and shoulders; Proposed lane widths and other critical dimensions; Existing / proposed traffic signal poles and signage; and Location of utilities. For signage and pavement marking proposals, a concept plan may not be required if a clear description of the scope of works is provided.

Step 3.5 Prepare Cost Estimate

Prepare a preliminary estimate with costs to be itemized generally as follows: Project development & survey; Land acquisition and resettlement; Alterations to utilities; Roadworks; Remedial environmental works; Signages and linemarkings; Street lighting; Traffic signal installation / alterations; Contingency; and Project management.

Page 31


Step

Explanation

Step 3.6

Prepare a report to document the outcome of the investigation and provide details of the candidate project.

Write an Accident Blackspot Report

Provide details as set out in the report format in Appendix I.

Page 32


APPENDICES

APPENDIX A Typical TARAS Rank report & map of accident locations.

APPENDIX B Example of TARAS Listing report

APPENDIX C Example of TARAS Summary Report

APPENDIX D Sample of a completed Traffic Accident Report (TAR)

APPENDIX E Chart of Traffic Accident Description (TAD) codes

APPENDIX F Typical Accident Factor Chart

APPENDIX G Typical Site Inspection Field Notes format

APPENDIX H Sample preliminary cost estimate

APPENDIX I Typical Accident Blackspot Report Format

APPENDIX J Accident Blackspots Ranking Spreadsheet for Site Data and Project Evaluation

Page 33

Accident Blackspot Investigation Handbook

Recommend Documents